Danfoss APP 2.5 Instruction Manual - Page 3

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Danfoss APP 2.5 Instruction Manual
Instruction
1.
Identification
2.

System design

APP pump instruction APP 0.6-1.0, APP 1.5-2.5 and APP 3.0-3.5
The design of the system must ensure that self
emptying of the pump during standstill is
avoided.
The inlet pressure of the pump must never
exceed the outlet pressure. This may typically
occur in boosted or open-ended systems with
direct water supply.
In order to avoid this it is recommended to install
a pre-stressed check valve or a pressure switch in
the pump inlet.
The opening pressure of the check valve must be
bigger or equal to the inlet pressure.
2.1 Open-ended systems with water supply
from a tank
(The numbers 1-3 refer to the drawing below.)
In order to eliminate the risk of cavitation,
observe the following guidelines:
1)
Place the tank above the pump (water level
in the tank should always be above the
pump).
2)
Place the inlet filter before the tank.
3)
Dimension the inlet line to obtain mini-
mum pressure loss (large flow area,
minimum pipe length, minimum number
of bends/connections, fittings with small
pressure losses).
180R9065 / 521B0733 / DKCFN.PI.013.C4.2T / 09.2012
2.2 Open-ended systems with direct water
supply
The pump is supplied with water direct from a
booster pump.
The water pressure must not exceed 5 bar abs.
(72.5 psi).

2.3 Problems with reversing pumps

If exposed to high pressure in the outlet while
the electric motor is not energized, the pumps
will start spinning backwards. This will not harm
the pumps as long as the pressure in the inlet
does not exceed the max. pressure of 5 bar.
If a non-return valve is mounted in the inlet line,
a low-pressure relief valve will also be required.
Alternatively a high-pressure check valve could
be mounted in the pump discharge line to
prevent the pump from reversing.
The dotted setup ensures that the inlet pressure
does not exceed the 5 bar abs., when a non-
return valve is mounted in the inlet.
6 bar
[87 psi]
3